Embodiments of the invention provide an apparatus which provide good RF uniformity within a processing chamber. In one embodiment, an apparatus includes a substrate support assembly, a terminal, and a dielectric insulator. The substrate support assembly has a center passage formed along a center axis. An RF transmission line is provided. The RF transmission line has a substantially vertical portion and a substantially horizontal portion, wherein the terminal is coupled to the substantially horizontal portion of the RF transmission line. The dielectric insulator circumscribes the substantially horizontal portion of the RF transmission line. The dielectric insulator has a first opening through which the terminal passes.